These studies comprised two parts. (1) A double-blind crossover study of digitalis in patients with stable congestive heart failure (CHF) and sinus rhythm showed that digitalis could be discontinued for three months without adverse clinical effect and only a 3 per cent increase in resting heart size and 10 per cent decline in velocity of fiber shortening. The new dimension to this aspect of the study is that long-term follow-up (11-33 mo) of these patients has verified our favorable initial experience in discontinuing digitalis. (2) We have recently compared the effects of a digitalis intravenous bolus in healthy young and elderly men, employing systolic time intervals as a monitor of the inotropic effect and have found no age effect.